GEOTECHNICAL INVESTIGATION PROPOSED EASTGATE Subject: Geotechnical Investigation Proposed Eastgate Building

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  • GEOTECHNICAL INVESTIGATION PROPOSED EASTGATE BUILDING 1

    SWC Perimeter Road and 99th Street San Bernardino, California

    for Hillwood

  • 22885 Savi Ranch Parkway  Suite E  Yorba Linda  California  92887 voice: (714) 685-1115  fax: (714) 685-1118  www.socalgeo.com

    May 23, 2018

    Hillwood 901 Via Piemonte, Suite 175 Ontario, California 91764

    Attention: Mr. Joshua Cox Development Director

    Project No.: 18G144-1

    Subject: Geotechnical Investigation Proposed Eastgate Building 1 SWC Perimeter Road and 99th Street San Bernardino, California

    Gentlemen:

    In accordance with your request, we have conducted a geotechnical investigation at the subject site. We are pleased to present this report summarizing the conclusions and recommendations developed from our investigation.

    We sincerely appreciate the opportunity to be of service on this project. We look forward to providing additional consulting services during the course of the project. If we may be of further assistance in any manner, please contact our office.

    Respectfully Submitted,

    SOUTHERN CALIFORNIA GEOTECHNICAL, INC.

    Daniel W. Nielsen, RCE 77915 Senior Engineer

    Robert G. Trazo, GE 2655 Principal Engineer

    Distribution: (1) Addressee

  • Proposed Eastgate Building 1 – San Bernardino, CA Project No. 18G144-1

    TABLE OF CONTENTS

    1.0 EXECUTIVE SUMMARY 1

    2.0 SCOPE OF SERVICES 3

    3.0 SITE AND PROJECT DESCRIPTION 4

    3.1 Site Conditions 4 3.2 Proposed Development 4

    4.0 SUBSURFACE EXPLORATION 6

    4.1 Scope of Exploration/Sampling Methods 6 4.2 Geotechnical Conditions 6

    5.0 LABORATORY TESTING 8

    6.0 CONCLUSIONS AND RECOMMENDATIONS 10

    6.1 Seismic Design Considerations 10 6.2 Geotechnical Design Considerations 13 6.3 Site Grading Recommendations 14 6.4 Construction Considerations 18 6.5 Foundation Design and Construction 18 6.6 Floor Slab Design and Construction 20 6.7 Retaining Wall Design and Construction 21 6.8 Pavement Design Parameters 23

    7.0 GENERAL COMMENTS 26

    8.0 REFERENCES 27

    APPENDICES

    A Plate 1: Site Location Map Plate 2: Boring Location Plan

    B Boring Logs C Laboratory Test Results D Grading Guide Specifications E Seismic Design Parameters F Liquefaction Evaluation Spreadsheets

  • Proposed Eastgate Building 1 – San Bernardino, CA Project No. 18G144-1

    Page 1

    1.0 EXECUTIVE SUMMARY

    Presented below is a brief summary of the conclusions and recommendations of this investigation. Since this summary is not all inclusive, it should be read in complete context with the entire report.

    Geotechnical Design Considerations  Mapping performed by the California Geological Survey indicates that the subject site is

    located within a liquefaction hazard zone.  Our site-specific liquefaction evaluation indicates that the onsite soils are not subject to

    liquefaction during the design seismic event. No design considerations related to liquefaction are considered warranted for this project.

     Undocumented fill soils were encountered at some of the boring locations, extending from either the ground surface or from beneath the existing aggregate base materials to depths of 1½ to 3± feet. Boring No. B-2 was drilled at the top of a soil stockpile and encountered fill soils extending to a depth of about 10± feet, which is roughly equal to the height of the stockpile at that location.

     The fill soils and near surface alluvium possess variable strengths and densities. These soils, in their present condition, are not considered suitable for support of the foundation loads of the new structure. These soils are underlain by dense to very dense, high strength alluvial soils.

     Remedial grading will be necessary to remove the undocumented fill soils in their entirety as well as the upper portion of the near-surface native alluvium and replace these materials as compacted structural fill.

     The on-site soils possess varying amounts of oversized materials, including cobbles. Because grading will require excavation into these materials, consideration should be given to using selective grading techniques to remove the cobbles from these soils prior to reuse as fill. Recommendations regarding selective grading and handling of oversized materials are provided in Section 6.3 and Appendix D of this report.

    Site Preparation  Initial site preparation should include stripping of any surficial vegetation. At the time of

    subsurface exploration, localized areas of the site were sparsely vegetated with grass and weeds.

     Stockpiled demolition debris, including asphalt and concrete fragments should be disposed of off-site. Alternatively, concrete and asphalt debris may be pulverized to a maximum 2-inch particle size, well mixed with the on-site soils, and incorporated into new structural fills or it may be crushed and made into CMB.

     The soils within the proposed building area should be overexcavated to a depth of 3 feet below existing grade and to a depth of at least 3 feet below proposed building pad subgrade elevations. The depth of overexcavation should also be sufficient to remove any existing fill soils. The proposed foundation influence zones should be overexcavated to a depth of at least 2 feet below proposed foundation bearing grade.

     After overexcavation has been completed, the resulting subgrade soils should be evaluated by the geotechnical engineer to identify any additional soils that should be overexcavated.

  • Proposed Eastgate Building 1 – San Bernardino, CA Project No. 18G144-1

    Page 2

    The resulting soils should be scarified and thoroughly flooded to achieve a moisture content of 0 to 4 percent above optimum moisture, to a depth of at least 24 inches. The overexcavation subgrade soils should then be recompacted under the observation of the geotechnical engineer. The previously excavated soils may then be replaced as structural fill, compacted to 90 percent of the ASTM D-1557 maximum dry density.

     The new pavement and flatwork subgrade soils are recommended to be scarified to a depth of 12± inches, thoroughly moisture conditioned and recompacted to at least 90 percent of the ASTM D-1557 maximum dry density.

    Foundation Design Recommendations  Conventional shallow foundations, supported in newly placed compacted fill.  3,000 psf maximum allowable soil bearing pressure.  Reinforcement consisting of at least two (2) No. 5 rebars (1 top and 1 bottom) in strip footings.

    Additional reinforcement may be necessary for structural considerations.

    Building Floor Slab  Conventional Slab-on-Grade: minimum 6 inches thick.  Modulus of Subgrade Reaction: k = 150 psi/in.  Reinforcement is not necessary for geotechnical considerations.  The actual thickness and reinforcement of the floor slab should be determined by the

    structural engineer.

    Pavements

    ASPHALT PAVEMENTS (R = 50)

    Materials

    Thickness (inches)

    Auto Parking and Auto Drive Lanes (TI = 4.0 to 5.0)

    Truck Traffic

    TI = 6.0 TI = 7.0 TI = 8.0 TI = 9.0

    Asphalt Concrete 3 3½ 4 5 5½

    Aggregate Base 3 4 5 5 7

    Compacted Subgrade 12 12 12 12 12

    PORTLAND CEMENT CONCRETE PAVEMENTS (R = 50)

    Materials

    Thickness (inches)

    Autos and Light Truck Traffic (TI = 6.0)

    Truck Traffic

    TI = 7.0 TI = 8.0 TI = 9.0

    PCC 5 6 7 8

    Compacted Subgrade (95% minimum compaction)

    12 12 12 12

  • Proposed Eastgate Building 1 – San Bernardino, CA Project No. 18G144-1

    Page 3

    2.0 SCOPE OF SERVICES

    The scope of services performed for this project was in accordance with our Proposal No. 18P130R2, dated April 19, 2018. The scope of services included a visual site reconnaissance, subsurface exploration, field and laboratory testing, and geotechnical engineering analysis to provide criteria for preparing the design of the building foundations, building floor slab, and parking lot pavements along with site preparation recommendations and construction considerations for the proposed development. Based on the location of the subject site, this investigation also included a site-specific liquefaction evaluation. The evaluation of the environmental aspects of this site was beyond the scope of services for this geotechnical investigation.

  • Proposed Eastgate Building 1 – San Bernardino, CA Project No. 18G144-1

    Page 4

    3.0 SITE AND PROJECT DESCRIPTION

    3.1 Site Conditions

    The site is located on the southwest corner of Perimeter Road and 99th Street in San Bernardino, California. The site is bounded to the north by Perimeter Road, to the west by a parking lot, to the south by the San Bernardino International Airport, and to the east by 99th Street. The general location of the site is illustrated on the Site Location Map, enclosed as Plate 1 in Appendix A of this report.

    The subject site consists of multiple parcels which total 52± acres in size. The site is presently used as two (2) tractor trailer parking/storage lots which are separated by a chain-link fence. The eastern ¾± of the site consists of a large tractor trailer parking/storage lot. A portion of a taxiway for the San Bernardino International Airport extends from the southwest into the southern portion of this section of the site. With the exception of two large stockpiles, the ground surface cover throughout the eastern ¾± of the subject site generally consists